1. Field of the Invention
This invention relates to a method for the aseptic collection of blood from an animal carcass.
2. The Prior Art
Blood serum is the clear liquid which is separated from the clot and cellular elements of the blood. Fetal bovine serum is known for its embryonic protein constituents which stimulate cell attachment and growth and, therefore, used extensively as a supplement to nutrient media used in mammalian cell culture. One use of such cultures is the production of viral vaccines. In addition, for an as yet unexplained reason, antibodies which tend to interfere with virus cultures are less likely to pass through the placenta of the bovine host into its fetus.
Recently, scientists have found that many live virus vaccines were contaminated with bacteriophages or phages (viruses that infect bacteria). Phages are introduced with the host bacteria that contaminate the fetal bovine serum which is, historically, collected in the extremely contaminated atmosphere of slaughterhouse. Contamination as high as 10.sup.8 bacteria per milliliter of serum has been found in serum so collected. Millipore filtration of the serum is used to remove these bacteria from the serum but phages pass through the filter and remain in the serum.
The effects of the presence of phages in the serum have not been completely determined although it is believed by some that certain phages may routinely infect human cells and cause diseases. Accordingly, there is considerable concern developing with respect to its presence in live virus vaccines. For example, see "Phage in Live Virus Vaccines: Are They Harmful to People?", Science, Volume 187, pages 522, 523 (Feb. 14, 1975).
Chemical contaminants present in the body fluids and any chemical sterilants may inadvertently enter the blood during collection. These chemical contaminants readily pass with the serum through the filter and are present in the serum when the serum is ultimately used as a nutrient medium for live virus vaccines.
Bovine fetuses are readily and abundantly available in most slaughterhouse operations and the fetus is commonly referred to in the jargon of the slaughterhouse as the "slunk". During the slaughter operation, the slunk is diverted to a collection area on or adjacent the slaughtering or kill floor for fetal blood collection. At the collection site a technician collects the fetal blood according to various conventional techniques.
Historically, the technician severs the umbilical cord near its midpoint and places both of the severed ends in the open mouth of a collection bottle. Fetal blood from both the placenta and the fetus is drained into the bottle by the technician "milking" both lengths of umbilical cord. This method resulted in (1) low volumes of collected blood and (2) exposure of the blood to contamination from (a) the atmosphere of the slaughtering operation, (b) chemicals in the body fluids on the umbilical cord and any chemical sterilants used on the umbilical cord and (c) fetal wastes (feces and urine) in the umbilical cord.
A recent advancement in fetal blood collection apparatus incorporates a closed loop vacuum collection system wherein an evacuated, rigid collection bottle serves as the suction source for a hollow needle connected to the bottle by a length of tubing. The needle is first inserted into the fetal cardiovascular system and then connected to the vacuum bottle. This system is readily susceptible to obstruction by clot formation and/or tissue fragments in the small diameter lumen of the needle and connective tubing. Obstructions are customarily cleared by withdrawing the needle to permit the vacuum to suck it through the system into the bottle. After the system is cleared, the needle is reinserted for continued aspiration of blood.
Removal of the needle permits exposure of the needle to bacterial contaminants in the extremely contaminated atmosphere of the slaughterhouse and to chemical contaminants in the normal fetal environment and any chemical sterilants present on the surfaces adjacent the puncture site. Reinsertion of the needle results in the consequent inoculation of the cardiovascular system with these contaminants. Additionally, aspiration of slaughterhouse atmosphere significantly increases the opportunities for bacterial contamination of the collected blood.
In view of the foregoing, what is needed is an aseptic blood collection technique which eliminates the difficulties and problems inherent in both the severed umbilical cord collection technique and the closed loop vacuum collection system. The improved collection system should (1) utilize gravity flow collection to eliminate the need for a vacuum system; (2) collect blood available in both the placenta and the fetus cardiovascular system; (3) accommodate fetus manipulation to stimulate additional blood drainage; and (4) provide for aseptic collection of the fetal blood. The gravity system should also accommodate collection of the blood into flexible bags which permit blood clot manipulation to release serum entrapped in the clot. Such a system is disclosed and claimed herein.